Embodiment in accordance with the present invention relates to a radio frequency identification (RFID) device which is capable of automatically identifying an object by communicating with an external reader.
An RFID is a contactless identification technology which can automatically identifies an object by using a radio signal. Specifically, an RFID tag is attached to an object to be identified, and the RFID tag communicates with an RFID reader through transmission/reception of a radio signal. In this manner, the identification of the object is achieved. The use of the RFID can overcome the shortcomings of a conventional automatic identification technology, such as a barcode and an optical character recognition technology.
In recent years, RFID tags have been used in various fields, such as a distribution management system, a user authentication system, an electronic cash system, a traffic system, and so on.
For example, a distribution management system performs a commodity classification or an inventory management by using integrated circuit (IC) tags (in which data are recorded) instead of a delivery statement or tag. In another example, a user authentication system performs a room management by using IC cards in which personal information is recorded.
Meanwhile, a memory used in the RFID tag may be implemented with a nonvolatile ferroelectric memory.
In general, a nonvolatile ferroelectric memory (i.e., a ferroelectric random access memory (FeRAM)) is considered by many as a next generation storage device because it has a data processing speed similar to that of a dynamic random access memory (DRAM) and data is retained even when power is interrupted.
The FeRAM has a structure substantially similar to that of the DRAM but uses a ferroelectric capacitor as a storage element. Ferroelectric has a high remnant polarization characteristic. As a result, data is not erased even though an electric field is removed.
FIG. 1 illustrates an overall structure of a general RFID device.
The RFID device includes an antenna unit 1, an analog unit 10, a digital unit 20, and a memory unit 30.
The antenna unit 1 receives a radio signal transmitted from an external RFID reader. The radio signal received through the antenna unit 1 is inputted to the analog unit 10 through antenna pads 11 and 12.
The analog unit 10 amplifies the inputted radio signal and generates a power supply voltage VDD which can then be used as a driving voltage of an RFID tag. The analog unit 10 detects an operation command signal CMD from the inputted radio signal, and outputs the command signal CMD to the digital unit 20. In addition, the analog unit 10 detects the output voltage VDD and outputs a power on reset signal POR and a clock CLK to the digital unit 20. The power on reset signal POR is a signal which controls a reset operation.
The digital unit 20 receives the power supply voltage VDD, the power on reset signal POR, the clock CLK, and the command signal CMD from the analog unit 10, and outputs a response signal RP to the analog unit 10. In addition, the digital unit 20 outputs an address ADD, an input/output data I/O, a control signal CTR, and the clock CLK to the memory unit 30.
The memory unit 30 reads, writes and stores data by using a memory device.
The RFID device uses several frequency bands, and the device characteristics vary depending on the frequency bands. In general, as the frequency band is lowered, the recognition speed of the RFID device becomes slower, and the RFID device operates with a shorter distance and is less influenced by the environment. On the other hand, as the frequency band becomes higher, the recognition speed of the RFID device becomes faster, and the RFID device operates at a longer distance and is greatly influenced by the environment.
When a distance between the external reader and the RFID device is far, a weak radio signal is inputted to the RFID device. The inputted weak radio signal may not reach a level at which a Schottky diode or the like provided inside a demodulator can be driven. In this case, the long-distance recognition performance of the RFID device is deteriorated.
Furthermore, when the conventional RFID device outputs a response signal RP through the antenna unit 1 to the external reader, a radio signal RF is generated by using an internal oscillator provided in the RFID device. In this case, due to the power requirements of the separate internal oscillator, power consumption increases and the circuit of the RFID device becomes complicated.